Breast cancer tumors are classified as either estrogen-receptor positive (ER+) or estrogen-receptor negative (ER-). Classification procedures are well-known and include measurement of intracellular receptor protein by either a steroid-binding assay or by immunochemical assay or by measuring mRNA corresponding to said protein using Northern blot analysis. The term "estrogen-receptor positive breast cancer" is used herein to denote the disorder of those patients who were determined to have estrogen-receptor positive (ER+) breast cancer tumors prior to primary treatment. The term "estrogen-receptor negative breast cancer" is used herein to denote the disorder of those patients who were determined to have estrogen-receptor negative (ER-) breast cancer tumors prior to primary treatment.
Primary treatment in the case of those determined to have estrogen-receptor positive breast cancer tumors or estrogen-receptor negative breast cancer tumors is mastectomy or breast conserving surgery (lumpectomy, tylectomy, wide excision, partial mastectomy, or quadrantectomy) plus radiation therapy.
Adjuvant systemic therapy is begun soon after primary therapy to delay recurrence and/or to prolong survival. One kind of adjuvant systemic therapy is adjuvant chemotherapy, e.g., using a combination regimen of cyclophosphamide, methotrexate and 5-fluorouracil, e.g., for four to 24 months. Another kind of adjuvant systemic therapy is adjuvant tamoxifen therapy given for two to five years. Adjuvant chemotherapy is given routinely to all premenopausal, node-positive patients. Adjuvant tamoxifen therapy is given routinely to post-menopausal women who are node-positive and have estrogen-receptor positive tumors.
Patients with metastatic disease are treated with endocrine therapy or chemotherapy or in some cases with radiation therapy to palliate symptoms.
The method of the invention offers an alternative or supplement to chemotherapy and tamoxifen therapy for adjuvant therapy and for the first time offers an adjuvant therapy treatment different from normal relatively toxic chemotherapy for those with estrogen-receptor negative breast cancer. Moreover, the method of the invention offers an alternative or supplement to chemotherapy, endocrine therapy and radiation therapy in the treatment of metastatic disease.